first thing to check, what are the permissions on
openemr/interface/main/calendar/modules/PostCalendar/pntemplates/cache
&
openemr/interface/main/calendar/modules/PostCalendar/pntemplates/compiled
?
If your web server user doesn’t have read write access to those directories you can have calendar issues.
Have you run mysqlcheck on your db in case there’s a problem with the table?
You mentioned that you customized something, is it related to the calendar?
Just wondering, because in general we don’t see things like this happen with a properly set up install of OpenEMR.
The first thing I noticed is all of the modifications that you made to the pop up window when you click a time to schedule.
It seems that you removed most of the items from the window which the calendar may use when it creates the appointment / reservation. If the code that is written to post a new appointment is looking for any of the items you removed it would not post anything. You may want to check your logs and look for any errors that are created when you try to create a new posting.